Telomerase activity in primary and secondary glioblastomas multiforme as anovel molecular tumor marker

Object. Telomerase activity is responsible for cell immortality. To examine the role of telomerase in the carcinogenesis of human glioblastomas multif orme (GBMs), the authors studied telomerase activity, telomerase component expression, and telomere lengths in 42 GBM samples. Methods. In all samples, EGFR and MDM2 amplifications and overexpressions w ere examined using Southern and Northern blot analyses. The p53 mutation wa s analyzed using polymerase chain reaction-single strand conformational pol ymorphism and by direct sequence analysis. Specimens of tissues were immuno stained with p53, EGFR, and MDM2 antibodies. Allelic loss on chromosomes 17 p and 10 was assessed by loss of heterozygosity (LOH) assays. Telomerase ac tivity, expression of its components (human telomerase reverse transcriptas e [hTERT], human telomerase RNA component [hTERC], and telomerase-associate d protein [TEP1]), and telomere lengths were analyzed using the telomeric r epeat amplification protocol (TRAP)-hybridization protection assay, reverse transcription-polymerase chain reaction, and Southern blot analysis. Accor ding to the results of assessments of EGFR and MDM2 amplifications, p53 mut ation, LOHs in chromosomes 17p and 10, and the clinical course of the disea se, the 42 samples were classified into 22 primary and 20 secondary gliobla stomas. Twenty-six (61.9%) of all 42 samples demonstrated detectable telomerase act ivity during the TRAP assay. Secondary GBMs displayed significantly higher levels of telomerase activity and hTERT expression than primary GBMs. Tumor s with a p53 gene mutation demonstrated significantly higher telomerase act ivity than those without a p53 mutation. Four samples with a codon 175 muta tion demonstrated an exceptionally high amount of telomerase activity. In s econdary GBMs, the increase in telomerase activity and the hTERT expression level correlated with the increased frequency of p53 mutations. There was no significant difference in telomere length between primary and secondary GBMs. Conclusions. These results suggest that telomerase activity and p53 mutatio ns both play important roles in the multistep carcinogenesis of GBMs. Telom erase activity and hTERT expression may be considered as novel distinctive factors in human GBMs.